tikzposter and hyperref error

When you use the tikzposter LaTeX class and also the hyperref package, and you encounter a compilation error similar to ! LaTeX Error: Loading a class or package in a group, then the following snippet in your preamble may resolve the issue:

\makeatletter
\patchcmd{%
    \Hy@AtBeginDocumentHook%
}{%
    \RequirePackage {color}%
}{}{}{%
    \PackageWarning{patch}{patch failed!}%
}
\makeatother

The core problem is that the tikzposter class puts all of the main content inside one big tikzpicture environment. More specifically, it starts a \begin{tikzpicture} in \AtBeginDocument but never closes it there.

Because of that, when hyperref tries to load the color package through its own \AtBeginDocument, that package ends up being loaded inside the still-open tikzpicture environment. That’s what triggers the error about loading a class or package “in a group.”

The fix we used basically prevents hyperref from trying to load color during its custom \AtBeginDocument to resolve the conflict.